Many products currently marketed and sold to consumers are designed for limited use. These products are usually associated with a single event, a restricted time period or restricted access. There are many reasons for the need of single use or limited use products.
An example of a single use product is a disposable syringe. Instrument contamination and cross infection between patients is an ever present concern if the syringe is inadvertently reused. It is a particular concern in some countries where repeated use of instruments is known to transmit serious diseases such as HIV and hepatitis. Medical and ophthalmic devices that must be sterilized such as scalpels or tonometers (for the measurement of a patient's intraocular pressure) body piercing and tattooing instruments used on multiple clients also give cause for concern. Needles used in acupuncture offer another example. Decontamination procedures or employment of single-use devices are methods used to control cross infection, but they rely on personnel awareness, willingness to follow protocol, monitoring and documentation.
The limited use type of product is usually associated with goods that should be used for a restricted time period. One example of this type of product is “daily wear” or disposable contact lenses. Contact lenses for refractive correction or cosmetic purposes require suitable wear and care regimes in order to maintain good eye health. Non-compliance on the part of the patient, either through choice or due to lack of education, can injure the eye. Frequent replacement lenses are sometimes worn for longer than recommended or they may be stored or cleaned inappropriately.
A number of patents have tried to address the requirements for single use, limited use, or restricted access products.
U.S. Pat. No. 3,899,295 describes the use of an indicator containing a pH sensitive dye applied to the container of a product such as a medical instrument. The indicator displays a first color in a normal atmosphere, then following introduction of a basic atmosphere the sensor displays a second color. The problem with this patent is that the indicator is not displaying information relating to the condition of the product contained within the package. Since the indicator is not incorporated within or fixed onto the product, the information given actually relates to the container, not its contents. An additional problem with this patent is that the basic atmosphere in which the product is stored is chlorine gas which is highly reactive to the materials that comprise many of the products that one could imagine being supplied in a sterile package container, such as metal surgical instruments and many pharmaceutical compounds or drugs.
Similarly, U.S. Pat. No. 4,098,577 by the same inventor describes a similar pH sensitive indicator and two different atmospheric conditions, however that invention describes the indicator change in the presence of an acidic atmosphere. As described above, the indicator is not incorporated within or fixed onto the product, therefore the information presented by the indicator relates to the container, not its contents.
U.S. Pat. No. 4,526,752 presents a tamper resistant package with an indicator means. The invention describes a container which incorporates an indicator within its structure to display information on whether a container has been previously opened. As with other patents, the indicator relates to the condition of the package and not the product contained in the package.
U.S. Pat. No. 6,790,411 describes a solution based hydrogen peroxide indicator where the solution has a first color in normal atmospheric conditions, then following a sterilization process using hydrogen peroxide, the solution exhibits a second color. One will certainly recognize a problem with this technique by considering the case where a package that has been sterilized with hydrogen peroxide, is subsequently tampered with, punctured, or otherwise damaged and made non sterile, while the indicator still displays the sterile condition.
U.S. Pat. No. 6,851,808 describes an ophthalmic lens product with an attached indication means that provides the user information relating to the products condition or previous use. The invention overcomes many of the problems with the previously described patents. However, since the indicator means described in the patent uses changes in the product's light environment as the initiator for the use indication display, and since variations exist in the lighting environment where the product is used, the use indication can present at a rate that is faster or slower than that which is optimally desired.
Many products currently marketed and sold to consumers are supplied prepackaged where the packaging is intended to preserve the freshness of the product or in the case of medication, the potency of the content within the packaging. These products are usually associated with a single event, i.e., the contents remain fresh or potent until the packaging is opened by the consumer.
An example of the importance of preservation of a packaged product is a cold tablet or a food item. Medicinal potency or food spoilage and the expense related to these issues are important to both consumers and manufacturers. Pharmaceuticals, food stuff, and similar items are commonly packaged in sealed plastic containers.
Atmospheric oxygen permeation through the plastic material of the container negatively affects the freshness of the contents of many packaged products. In the case of pharmaceuticals, oxygen absorption decreases potency. In the case of food products, oxygen absorption into the packaged food makes the food taste stale.
A number of patents have tried to address the requirements for packaging environment condition:
U.S. Pat. No. 4,285,697 describes the use of a spoilage indicator applied to the food within a container. The indicator displays a color indication in response to various gases generated by the spoiled food. The indicator must be in contact with the product within the packaging. This patent does not describe a means to display the possible range of conditions about the packaged contents, such as good, acceptable or bad.
Similarly, U.S. Pat. No. 4,003,709 presents a method to indicate the deterioration of food within a package by detecting CO2. This indicator does not have the possibility to indicate a range of freshness of the contents within the package.
U.S. Pat. No. 4,526,752 presents a tamper resistant package with an indicator means. The invention describes a container which incorporates an indicator within its structure to display information on whether a container has been previously opened. As with other patents, the indicator relates to whether the package has been opened or not, and not the condition of the unopened package and its contents.
U.S. Pat. No. 6,790,411 describes a solution based hydrogen peroxide indicator where the solution has a first color in normal atmospheric conditions, and then following a sterilization process using hydrogen peroxide, the solution exhibits another color. A package that has been sterilized with hydrogen peroxide, is subsequently tampered with, punctured, or otherwise damaged and made non sterile, would still display an indication of sterile conditions with this type of indicator.
U.S. Pat. No. 8,241,918 describes a freshness indicator for beverages using electronic data means and comparing the data via a processing unit to previously stored freshness criteria. This method is complex and expensive.